Polymer safety glazing for vehicles

ABSTRACT

A laminate includes a polycarbonate substrate and an ultraviolet hard coat film disposed on the polycarbonate substrate. The ultraviolet hard coat film may include a polyethylene terephthalate (PET) layer, an adhesive interposed between the PET layer and the polycarbonate substrate, and an exterior hard coat disposed on the PET layer opposite the polycarbonate substrate. The exterior hard coat may include UV stabilizers. The laminate may include additional ultraviolet hard coat films stacked on the ultraviolet hard coat film. The laminate may be thermoformed into the shape of a curved vehicle windshield.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to and claims the benefit of U.S. ProvisionalApplication No. 62/850,966, filed May 21, 2019 and entitled “POLYMERSAFETY GLAZING FOR VEHICLES,” the entire contents of which is expresslyincorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND 1. Technical Field

The present disclosure relates generally to safety glazing and, moreparticularly, to polymer safety glazing for vehicle windows includingwindshields.

2. Related Art

Safety glazing has historically been made of glass. Glass has a hardnessthat can withstand scratching from windshield wipers and some amount ofabrasive debris. It is also very economical and lends itself to massproduction techniques. However, glass breaks easily and can presentdangerous sharp pieces that can lacerate passengers, causing personalinjuries. This problem has been mitigated to a point by tempering,causing the glass to break into small pieces (½″), and by laminating twoglass pieces together with a flexible polymer polyvinylbutyral (PVB)core between them in an attempt to hold the small fragments together.

Unfortunately, glass safety glazing is susceptible to pitting by smallaggregates and dust in the air, causing obscured vision while travelingtoward the sun. Over 15 million glass windshields are replaced each yearfor pitting and breaking in the USA alone. Moreover, laminatedglass-PVB-glass windshields cannot be recycled because the PVB corecontaminates the glass.

Considering the drawbacks of glass safety glazing, laceration ofpassengers remains a longstanding problem with no ideal solution. Forexample, 30 years of research has attempted to place a polymer coatingor layer on the interior of a glass windshield without any commercialsuccess.

Polycarbonate exhibits superior impact resistance and is used forvehicle glazing in auto racing and off-road vehicles. However,polycarbonate is so soft a material that it scratches and pits tooeasily for use in commercial or public vehicles. To date, there is noavailable direct hard coating to overcome these durability issues.Therefore, polycarbonate windshields are currently restricted tomotorcycles on public roads. For example, Saudi Basic IndustriesCorporation (SABIC) is the producer of LEXAN branded polycarbonate. Intheir 2016 Department of Transportation (DOT) Guidebook regarding LEXANsheet products, they state, “Except for motorcycle windshields, SABIC'sthermoplastics materials generally cannot be used for forward facingexterior glazing . . . .”

BRIEF SUMMARY

The present disclosure contemplates various systems and methods forovercoming the above drawbacks accompanying the related art. One aspectof the embodiments of the present disclosure is a laminate including apolycarbonate substrate and an ultraviolet hard coat film disposed onthe polycarbonate substrate. The ultraviolet hard coat film may includea polyethylene terephthalate (PET) layer, an adhesive interposed betweenthe PET layer and the polycarbonate substrate, and an exterior hard coatdisposed on the PET layer opposite the polycarbonate substrate. Theexterior hard coat, the PET layer, and/or the adhesive may include UVstabilizers.

The polycarbonate substrate may be 3-8 mm thick. The PET layer may be2-6 mil thick. The exterior hard coat may be 2-10 microns thick. Theexterior hard coat may have a gouge pencil hardness of greater than 8H.The adhesive may be a pressure sensitive adhesive.

The laminate may include an interior hard coat disposed on thepolycarbonate substrate opposite the PET layer. The interior hard coatmay have a gouge pencil hardness of 6H to 8H.

The ultraviolet hard coat film may be a first of a plurality ofultraviolet hard coat films stacked on the polycarbonate substrate. Theplurality of ultraviolet hard coat films may include a secondultraviolet hard coat film disposed on the first ultraviolet hard coatfilm, the second ultraviolet hard coat film including a second PETlayer, a second adhesive interposed between the second PET layer and thefirst ultraviolet hard coat film, and a second exterior hard coatdisposed on the second PET layer opposite the first ultraviolet hardcoat film. The second exterior hard coat, the second PET layer, and/orthe second adhesive may include UV stabilizers. The adhesive of thefirst ultraviolet hard coat film may be stronger than the secondadhesive.

The laminate may be thermoformed into the shape of a curved vehiclewindshield.

Another aspect of the embodiments of the present disclosure is a method.The method may include depositing a UV stabilized hard coat on a firstside of a polyethylene terephthalate (PET) carrier, coating a secondside of the PET carrier, opposite the first side, with an adhesive, andadhering the second side of the PET carrier to a polycarbonate substrateusing the adhesive.

The PET carrier, the UV stabilized hard coat, and the adhesive maydefine an ultraviolet hard coat film. The method may include winding theultraviolet hard coat film on a roll prior to adhering the second sideof the PET carrier to the polycarbonate substrate. The method mayinclude applying a removable liner to the second side of the PET carrierafter the coating. The method may include removing the removable linerfrom the second side of the PET carrier prior to adhering the secondside of the PET carrier to the polycarbonate substrate. The method mayinclude thermoforming the polycarbonate substrate with the adheredultraviolet hard coat film to the shape of a curved vehicle windshield.

The PET carrier, the UV stabilized hard coat, and the adhesive maydefine a first ultraviolet hard coat film. The method may includedepositing a second UV stabilized hard coat on a first side of a secondPET carrier, coating a second side of the second PET carrier, oppositethe first side, with a second adhesive, and adhering the second side ofthe second PET carrier to the first ultraviolet hard coat film using thesecond adhesive. The adhesive of the first ultraviolet hard coat filmmay be stronger than the second adhesive. The second PET carrier, thesecond UV stabilized hard coat, and the second adhesive may define asecond ultraviolet hard coat film.

The method may include thermoforming the polycarbonate substrate withadhered first and second ultraviolet hard coat films to the shape of avehicle windshield. The method may include peeling off the secondultraviolet hard coat film to reveal the first ultraviolet hard coatfilm. The method may include depositing a new second UV stabilized hardcoat on a first side of a new second PET carrier, coating a second sideof the new second PET carrier, opposite the first side, with a newsecond adhesive, and adhering the second side of the new second PETcarrier to the first ultraviolet hard coat film using the new secondadhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout, and in which:

FIG. 1 shows a laminate that is thermoformed into the shape of a vehiclewindshield and installed in a vehicle according to an embodiment of thepresent disclosure;

FIG. 2 is a cross-sectional view of the laminate taken along the line2-2 in FIG. 1; and

FIG. 3 shows an example operational flow according to an embodiment ofthe present disclosure.

DETAILED DESCRIPTION

The present disclosure encompasses various embodiments of a laminate foruse as a vehicle windshield and a manufacturing method thereof. Thedetailed description set forth below in connection with the appendeddrawings is intended as a description of several currently contemplatedembodiments and is not intended to represent the only form in which thedisclosed invention may be developed or utilized. The description setsforth the functions and features in connection with the illustratedembodiments. It is to be understood, however, that the same orequivalent functions may be accomplished by different embodiments thatare also intended to be encompassed within the scope of the presentdisclosure. It is further understood that relational terms such as firstand second and the like are used solely to distinguish one from anotherentity without necessarily requiring or implying any actual suchrelationship in order between such entities.

FIG. 1 shows a laminate 100 that is thermoformed into the shape of avehicle windshield and installed in a vehicle 10 according to anembodiment of the present disclosure. FIG. 2 is a cross-sectional viewof the laminate 100 taken along the line 2-2 in FIG. 1. As shown in FIG.2, the laminate 100 may including a polycarbonate substrate 110 and oneor more ultraviolet hard coat films 120 (120 a, 120 b, etc.) disposed onthe polycarbonate substrate 110. By disposing the one or moreultraviolet hard coat films 120 on the polycarbonate substrate 110, thepolycarbonate substrate 110 can be protected from scratching and pittingby windshield wipers and debris during use. In this way, the laminate100 may combine the impact resistance of polycarbonate with thedurability needed for widespread vehicle use, all while avoiding thesafety hazards associated with glass windshields.

Unlike prior attempts to apply hard coating to polycarbonate, theultraviolet hard coat film 120 a includes a polyethylene terephthalate(PET) layer 122 a serving as a carrier, which may be adhered to thepolycarbonate substrate 110 by an adhesive 124 a interposedtherebetween. A UV stabilized exterior hard coat 126 a may be disposedon the PET layer 122 a opposite the polycarbonate substrate 110, withthe PET layer 122 a, adhesive 124 a, and exterior hard coat 126 adefining the ultraviolet hard coat film 120 a. The exterior hard coat126 a may have a gouge pencil hardness of greater than 8H, making thelaminate 100 far more durable than the polycarbonate substrate 110 wouldbe alone. By using the PET layer 122 a as a carrier, the exterior hardcoat 126 a can be applied without the difficulties that would arise ifone were to attempt to apply the exterior hard coat 126 a to thepolycarbonate substrate 110 directly. For example, the polycarbonatesubstrate 110 may be too soft to support the hard coat 126 a, thedifference in thermal expansion coefficient between the polycarbonatesubstrate 110 and the hard coat 126 a may cause the hard coat 126 a tofracture over time, and/or the hydrophilic quality of the polycarbonatesubstrate 110 may cause absorbed water to lift the hard coat 126 a.These concerns may be avoided by applying the hard coat 126 a to the PETlayer 122 a and allowing the PET layer 122 a to “float” on thepolycarbonate substrate 110 with the adhesive 124 a interposedtherebetween.

As shown in the example of FIG. 2, the ultraviolet hard coat film 120 amay be a first of a plurality of ultraviolet hard coat films 120 (120 a,120 b, etc.) stacked on the polycarbonate substrate 110. By way ofexample, a second ultraviolet hard coat film 120 b may include and bedefined by a PET layer 122 b, an adhesive 124 b, and an exterior hardcoat 126 b, which may be the same as the PET layer 122 a, adhesive 124a, and exterior hard coat 126 a, respectively, except that the adhesive124 b may be interposed between the PET layer 122 b and the firstultraviolet hard coat film 120 (e.g. the exterior hard coat 126 athereof). Additional (e.g. third, fourth, etc.) ultraviolet hard coatfilms 120 may be applied in the same way. When a laminate 100 havingmore than one ultraviolet hard coat film 120 becomes unacceptablydegraded over time during the life of the vehicle windshield or otherwindow (e.g. due to chips, oxidation, etc.), the outermost ultraviolethard coat film 120 may simply be peeled off and removed, revealing thefresh ultraviolet hard coat film 120 beneath. To this end, the adhesive124 a of the first ultraviolet hard coat film 120 a may be stronger thanthe adhesive 124 b etc. used for additional ultraviolet hard coat films120 (and in some cases the adhesives 124 b etc. may have furtherdecreasing strength with each additional ultraviolet hard coat film120). In this way, the first ultraviolet hard coat film 120 a may remainadhered to the polycarbonate substrate 110 while another ultraviolethard coat film 120 is peeled off. It is contemplated, for example, thatthe first ultraviolet hard coat film 120 a may be intended to remain onthe polycarbonate substrate 110 for the life of the laminate 100, withadditional hard coat films 120 being removable (and possiblyreplenishable as described below) as needed. Along the same lines, eachsuch additional ultraviolet hard coat film 120 beyond the first 120 amay be provided with a tab or other means for easy peel-away during thelife of the laminate 100.

The PET layer 122 a of the ultraviolet hard coat film 120 a may be 2-6mil thick (1 mil=1 thousandth of an inch) and may be, for example, abiaxially-oriented polyethylene terephthalate (BoPET) sold under theregistered trademark Mylar owned by the DuPont Company. The exteriorhard coat 126 a may be 2-10 microns (e.g. 5 microns) thick and may be,for example, a UV-curable polysiloxane-acrylic hybrid resin, such as aUV-curable resin marketed by DIC Corporation. In addition to having agouge pencil hardness of greater than 8H, the exterior hard coat 126 amay pass the abrasion test #18 specified in the American NationalStandards Institute (ANSI) Z26.1-1996 standard and the one-year weathertest #16 specified in the ANSI Z26.1-1996 standard. As noted above, theexterior hard coat 126 a may be UV-stabilized, for example, by theinclusion of UV stabilizers such as hydroxyphenyl-benzotriazole orhydroxyphenyl-triazine UV absorbers. By including UV stabilizers in theexterior hard coat 126 a, degradation of the PET carrier 122 a andadhesive 124 a caused by ultraviolet radiation in sunlight (e.g.yellowing or becoming brittle) can be prevented or slowed during thelife of the ultraviolet hard coat film 120 a. It is contemplated that UVstabilizers may be additionally or alternatively included in the PETcarrier 122 a and/or the adhesive 124 a. The adhesive 124 a may be 10-25microns (e.g. 25 microns) thick and may be, for example, a pressuresensitive adhesive (PSA) such as a low tack PSA having a peel strengthdetermined as a constant load per unit width needed for peeling of about30 grams per inch. The components of any additional ultraviolet hardfilms 120 beyond the first ultraviolet hard coat film 120 a may have thesame or similar specifications. The underlying polycarbonate substrate110 may be 3-8 mm (e.g. 4 mm) thick.

As shown in FIG. 2, the laminate 100 may further include an interiorhard coat 130 disposed on the polycarbonate substrate 110 opposite thePET layer 122 a. Because the interior hard coat 130 will be theinward-facing surface of the windshield, it will not be subject to thesame abrasions and impacts as the exterior hard coat 126 a and need notbe held to the same standards. As such, the interior hard coat 130 maybe softer than the exterior hard coat 126 a, thus mitigating thedifficulties discussed above with respect to directly applying theexterior hard coat 126 a to the polycarbonate substrate 110. Theinterior hard coat 130 may have a gouge pencil hardness of only 6H to8H, for example. The interior hard coat 130 need not necessarily passthe abrasion test #13 specified in the ANSI Z26.1-1996 standard or theone-year weather test #16 specified in the ANSI Z26.1-1996 standard.Like the exterior hard coat 126 a, the interior hard coat 130 may be2-10 microns (e.g. 5 microns) thick and may be, for example, aUV-curable polysiloxane-acrylic hybrid resin, such as a UV-curable resinmarketed by DIC Corporation. Because it will not be exposed directly tosunlight, the interior hard coat 130 may or may not have UV stabilizers.

FIG. 3 shows an example operational flow according to an embodiment ofthe present disclosure. The operational flow may begin with depositing aUV stabilized hard coat that will serve as an exterior hard coat 126 aon a first side of a PET carrier 122 a (step 310). The exterior hardcoat 126 a is preferably wet deposited onto the PET carrier 122 a butmay be applied according to any appropriate methods including spincoating, dip coating, or vacuum deposition. Before or after the exteriorhard coat 126 a is applied, the PET carrier 122 a may be coated on theopposite side with the adhesive 124 a (step 320). These three elements,the PET carrier 122 a, adhesive 124 a, and exterior hard coat 126 a, maybe permanently bonded to each other and can be collectively regarded asthe ultraviolet hard coat film 120 a. Once the adhesive 124 a is coatedon the PET carrier 122 a, a removable liner may be applied to the sameside of the PET carrier 122 a to protect the adhesive 124 a (step 330).The ultraviolet hard coat film 120 a may then be wound on a roll to forma roll-to-roll processing web that may be about 2 meters wide (step340). The operational flow of steps 310-340 may produce a roll of theultraviolet hard coat film 120 a at a rate of about 30 meters perminute.

As the ultraviolet hard coat film 120 a is unwound from the roll, theremovable liner may be removed to expose the adhesive 124 a (step 350),and the PET carrier 122 a may be adhered to the polycarbonate substrate110 by the exposed adhesive 124 a (step 360). For example, theultraviolet hard coat film 120 a may be dry nipped to the flatpolycarbonate substrate 110 by rollers. With the ultraviolet hard coatfilm 120 a having been adhered to the polycarbonate substrate 110, thelaminate 100 may be ready for thermoforming to the desired final shapeof the windshield or other window. However, as described above and shownin FIG. 2, the laminate 100 may include additional ultraviolet hard coatfilms 120 b, etc., which may later be peeled off one at a time as theydegrade with use. In this case, steps 310-360 may be repeated for eachadditional ultraviolet hard coat film 120, except that each subsequentultraviolet hard coat film 120 is adhered to the preceding ultraviolethard coat film 120 of the stack rather than to the polycarbonatesubstrate 110 in step 360. Once the desired number of ultraviolet hardcoat films 120 is stacked on the polycarbonate substrate 110, the entirelaminate 110 including the polycarbonate substrate 110 and one or moreadhered ultraviolet hard coat films 120 may be 2D or 3D thermoformed tocreate the windshield or other window (step 370). The thermoformingtemperature may be typically about 180 degrees Celsius and may utilize awindshield-shaped pattern or mold surface to form a properly sized 2D or3D shaped vehicle windshield for installation in a vehicle 10 (see FIG.1).

As explained above, it is contemplated that a laminate 100 having morethan one ultraviolet hard coat film 120 may allow for the outermostultraviolet hard coat film 120 to be peeled off and removed to reveal afresh ultraviolet hard coat film 120 beneath. In this respect, theoperational flow of FIG. 3 may continue during the life of the laminate100 that has been installed in a vehicle 10. When the outermostultraviolet hard coat film 120 becomes unacceptably degraded over time,it may be peeled off to reveal the next ultraviolet hard coat film 120underneath (step 380).

Following removal of one or more ultraviolet hard coat films 120 in step380, it is further contemplated that the set of ultraviolet hard coatfilms 120 may in some cases be replenished to avoid any degradation tothe first, innermost ultraviolet hard coat film 120 a and prolong thelife of the laminate 100. It is envisioned that this first ultraviolethard coat film 120 a would generally not be removed, as doing so wouldexpose the softer polycarbonate substrate 110 which may not conform tothe same standards for use in the vehicle 10. As such, the operationalflow of FIG. 3 may include a step of applying one or more newultraviolet hard coat films 120 to the first ultraviolet hard coat film120 a or to the remaining stack of ultraviolet hard coat films 120 (step390). For example, steps 310-360 may be performed for each additionalnew ultraviolet hard coat film 120, except that, in step 360, the newultraviolet hard coat film(s) 120 may be added to the laminate 100 whilethe laminate 100 is already installed in the vehicle 10 and thus afterit has been thermoformed. This may be done, for example, by wetlaminating the new ultraviolet hard coat film(s) 120 to the stack andshrinking them with a heat gun or blow dryer to conform them to theexisting shape of the laminate 100 while applying pressure using a cardor squeegee. In some cases, such additional ultraviolet hard coatfilm(s) may be applied using a sacrificial layer serving as a femalemold cavity as described in commonly owned U.S. application Ser. No.16/778,928, filed Jan. 31, 2020 and entitled “THERMOFORM WINDSHIELDSTACK WITH INTEGRATED FORMABLE MOLD,” the entire contents of which isexpressly incorporated herein by reference.

At the end of the life of the laminate 100, there is no contamination asin the case of conventional laminated glass-PVB-glass windshields. Thus,the polycarbonate substrate 110 can easily be recycled, resulting inless waste and benefiting the environment.

In the above examples of the laminate 100, it is assumed that at leastone ultraviolet hard coat film 120 is adhered to the polycarbonatesubstrate 110 prior to thermoforming into the desired shape of thewindshield or other window. However, the disclosure is not intended tobe so limited, and it is contemplated that the one or more ultraviolethard coat films 120 may be applied after the polycarbonate substrate 110is already thermoformed. For example, the same techniques describedabove in relation to replenishing the stack of ultraviolet hard coatfilms 120 in step 390 may be used to apply the original one or moreultraviolet hard coat films 120.

The above description is given by way of example, and not limitation.Given the above disclosure, one skilled in the art could devisevariations that are within the scope and spirit of the inventiondisclosed herein. Further, the various features of the embodimentsdisclosed herein can be used alone, or in varying combinations with eachother and are not intended to be limited to the specific combinationdescribed herein. Thus, the scope of the claims is not to be limited bythe illustrated embodiments.

What is claimed is:
 1. A laminate comprising: a polycarbonate substrate;and an ultraviolet hard coat film disposed on the polycarbonatesubstrate, the ultraviolet hard coat film including a polyethyleneterephthalate (PET) layer, an adhesive interposed between the PET layerand the polycarbonate substrate, and an exterior hard coat disposed onthe PET layer opposite the polycarbonate substrate, the exterior hardcoat including UV stabilizers.
 2. The laminate of claim 1, wherein thepolycarbonate substrate is 3-8 mm thick.
 3. The laminate of claim 1,wherein the PET layer is 2-6 mil thick.
 4. The laminate of claim 1,wherein the exterior hard coat is 2-10 microns thick.
 5. The laminate ofclaim 1, wherein the exterior hard coat has a gouge pencil hardness ofgreater than 8H.
 6. The laminate of claim 1, wherein the adhesive is apressure sensitive adhesive.
 7. The laminate of claim 1, furthercomprising an interior hard coat disposed on the polycarbonate substrateopposite the PET layer.
 8. The laminate of claim 7, wherein the interiorhard coat has a gouge pencil hardness of 6H to 8H.
 9. The laminate ofclaim 1, wherein the ultraviolet hard coat film is a first of aplurality of ultraviolet hard coat films stacked on the polycarbonatesubstrate, the plurality of ultraviolet hard coat films including asecond ultraviolet hard coat film disposed on the first ultraviolet hardcoat film, the second ultraviolet hard coat film including a second PETlayer, a second adhesive interposed between the second PET layer and thefirst ultraviolet hard coat film, and a second exterior hard coatdisposed on the second PET layer opposite the first ultraviolet hardcoat film, the second exterior hard coat including UV stabilizers. 10.The laminate of claim 9, wherein the adhesive of the first ultraviolethard coat film is stronger than the second adhesive.
 11. The laminate ofclaim 1, wherein the laminate is thermoformed into the shape of a curvedvehicle windshield.
 12. A method comprising: depositing a UV stabilizedhard coat on a first side of a polyethylene terephthalate (PET) carrier;coating a second side of the PET carrier, opposite the first side, withan adhesive; and adhering the second side of the PET carrier to apolycarbonate substrate using the adhesive.
 13. The method of claim 12,wherein the PET carrier, the UV stabilized hard coat, and the adhesivedefine an ultraviolet hard coat film, the method further comprisingwinding the ultraviolet hard coat film on a roll prior to the adhering.14. The method of claim 12, further comprising: applying a removableliner to the second side of the PET carrier after the coating; andremoving the removable liner from the second side of the PET carrierprior to the adhering.
 15. The method of claim 12, wherein the PETcarrier, the UV stabilized hard coat, and the adhesive define anultraviolet hard coat film, the method further comprising thermoformingthe polycarbonate substrate with the adhered ultraviolet hard coat filmto the shape of a curved vehicle windshield.
 16. The method of claim 12,wherein the PET carrier, the UV stabilized hard coat, and the adhesivedefine a first ultraviolet hard coat film, the method furthercomprising: depositing a second UV stabilized hard coat on a first sideof a second PET carrier; coating a second side of the second PETcarrier, opposite the first side, with a second adhesive; and adheringthe second side of the second PET carrier to the first ultraviolet hardcoat film using the second adhesive.
 17. The method of claim 16, whereinthe adhesive of the first ultraviolet hard coat film is stronger thanthe second adhesive.
 18. The method of claim 16, wherein the second PETcarrier, the second UV stabilized hard coat, and the second adhesivedefine a second ultraviolet hard coat film, the method furthercomprising thermoforming the polycarbonate substrate with the adheredfirst and second ultraviolet hard coat films to the shape of a vehiclewindshield.
 19. The method of claim 18, further comprising peeling offthe second ultraviolet hard coat film to reveal the first ultraviolethard coat film.
 20. The method of claim 19, further comprising:depositing a new second UV stabilized hard coat on a first side of a newsecond PET carrier; coating a second side of the new second PET carrier,opposite the first side, with a new second adhesive; and adhering thesecond side of the new second PET carrier to the first ultraviolet hardcoat film using the new second adhesive.